New data on the palaeobiology of the enigmatic yunnanozoans from the Chengjiang Biota, Lower Cambrian, China

58 1 January 45 70 10.1111/pala.12117

CONG, P.-Y., HOU, X.-G., ALDRIDGE, R.J., PURNELL, M.A., LI, Y.-Z. 2015. New data on the palaeobiology of the enigmatic yunnanozoans from the Chengjiang Biota, Lower Cambrian, China. Palaeontology, 58, 1, 45-70.

Pei-Yun Cong, Xian-Guang Hou, Richard J. Aldridge, Mark A. Purnell and Yi-Zhen Li
  • Pei-Yun Cong - Yunnan Key Laboratory for Palaeobiology, Yunnan University, Kunming, China (email: cong@ynu.edu.cn)
  • Xian-Guang Hou - Yunnan Key Laboratory for Palaeobiology, Yunnan University, Kunming, China (email: xghou@ynu.edu.cn)
  • Richard J. Aldridge* - Yunnan Key Laboratory for Palaeobiology, Yunnan University, Kunming, China
  • Richard J. Aldridge* - Department of Geology, University of Leicester, Leicester, UK
  • Mark A. Purnell - Department of Geology, University of Leicester, Leicester, UK (email: map2@le.ac.uk)
  • Yi-Zhen Li - Yunnan Key Laboratory for Palaeobiology, Yunnan University, Kunming, China
  • Yi-Zhen Li - State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, China

*Deceased

  • Issue published online: 7 JAN 2015
  • Article first published online: 9 JUN 2014
  • Manuscript Accepted: 5 MAY 2014
  • Manuscript Received: 12 NOV 2013
NSFC. Grant Numbers: 40962001, U1302232 Natural Science Foundation of Yunnan Province. Grant Number: 2009ZC008M Royal Society. Grant Number: JP081054 UK Natural Environment Research Council. Grant Numbers: NE/E015336/1, NE/K004557/1

Interpretation of the enigmatic soft-bodied yunnanozoans from the Lower Cambrian (Stage 3, Series 2) Chengjiang Biota has remained controversial for decades because of their strange body plan and their variable taphonomic alteration. Proposed affinities have ranged from stem bilaterian to stem vertebrate. A study of over seven hundred slabs, many newly collected, from five sections at two localities demonstrates that yunnanozoans have sclerotized dorsal and axial segments, a body cavity, a unique feeding region and a coiled alimentary canal. Although two genera have been previously discriminated, all specimens have the same number of filamentous arches (seven pairs) and of ventral circular structures (four pairs); this indicates that Haikouella Chen, Huang and Li, 1999 is a junior synonym of Yunnanozoon Hou, Ramsköld and Bergström, 1991. Our analysis reveals new details of the putative pharyngeal pores of Yunnanozoon lividum, and although there are similarities with the gill slits of deuterostomes, the question of their homology remains moot. The filamentous arches and their supporting rods were probably sclerotized and represent a specialized feeding structure. Yunnanozoans exhibit characters that are open to a number of alternative interpretations of putative homology, encompassing comparisons with deuterostomes and protostomes (including members of the Platyzoa). Given their unique features, and the current lack of secure homologies, the affinities of yunnanozoans should continue to be considered in a wider bilaterian context.

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